The present invention relates to an image recording material capable of recording images raised from sheet and having cubic effect, as well as an image processing method for recording and coloring images in three dimensions using the said recording material.
For forming images having cubic effect on sheet there have widely been used physical methods such as, for example, pressing sheet using a matrix. In addition, there has recently been adopted a method using a thermoexpansive sheet P which, as shown in sectional construction in FIG. 1, comprises a base sheet 1 and a coating layer 2 formed thereon, the coating layer 2 containing thermoexpansive microspheres 3 of a low boiling, vaporizable material each encapsulated in a thermoplastic resin microcapsule (see Japanese Examined patent publication No. 35359/84 and Japanese Laid-Open patent publication No. 101954/80).
For forming a three-dimensional image using the aforesaid thermoexpansive sheet, first a desired image is formed on the sheet using a material superior in light absorbing characteristic. For example, the image is formed with black toner using a conventional electrophotographic type copying machine. FIG. 2 (a) shows a state wherein images 4 have been formed with black toner on the coating layer 2 of the thermoexpansive sheet P. Then, the surface of the sheet P is irradiated with light, with the result that only the image portions 4 formed with black toner are heated selectively due to the difference in light absorbing characteristic, thereby causing the thermoexpansive microspheres 3 to expand. Consequently, the image portions are raised from the sheet surface to form images having cubic effect as shown in FIG. 2 (b).
Heretofore, a thermoexpansive sheet having three-dimensional images formed thereon has mainly been used as a braille sheet for visually handicapped people. In this case, a single color (black) was sufficient. On the other hand, sheets having three-dimensional images formed thereon are expected to be used as advertisement media, picture books and in various other applications. In this case, it is necessary that the three-dimensional images be colored and made large in area. If a color toner is used in the image forming process, however, since the color toner is lower in light absorbing efficiency than black toner, it does not generate heat sufficient to fully expand the thermoexpansive spheres on the sheet, thus making it difficult to form images having cubic effect.
To solve this problem there has been proposed a method wherein images are formed with black toner and raised by light irradiation, then a laminate film having a heat-transferable coloring material layer is pressure-bonded under heating to the sheet having the images thereon and thereby transferred to the raised toner images. According to this method, however, the toner image surfaces are cracked when raised and so become rough, resulting in that not only it is no longer possible to effect uniform transfer of the coloring material layer but also, since the coating layer is basically a thermoplastic resin, it easily bonds to an adhesive layer of the laminate film so there is fear of the coloring material layer also adhering to the other sheet surface portion than the toner image area and thereby staining the sheet surface.